Methionine lyase has a wide range of industrial and medical applications. In industry field, methionine lyase uses methionine as substrate to conduct direct catalytic synthesis of methyl mercaptan, and dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide as its derivatives. These sulfur compounds are important food additives spices, mainly for preparation of corn, tomatoes, potatoes, milk, pineapple and orange types of fruit flavor and fragrant flavor (Martinez-Cuesta Mdel, C., Pelaez, C., Requena, T., 2013. Methionine metabolism: major pathways and enzymes involved and strategies for control and diversification of volatile sulfur compounds in cheese. Crit Rev Food Sci Nutr. 53, 366-385.); Further, main product of methyl mercaptan is also an important fuel additive, while it can be used as a precursor compound for producing methionine and insecticides (Gutierrez, O. Y, Zhong, L. S., Zhu, Y. Z., Lercher, J. A., 2013. Synthesis of methanethiol from CS2 on Ni—, Co—, and K-Doped MoS2/SiO2 catalysts. Chemcatchem. 5, 3249-3259; Zhang, Y. H., Chen, S. P., Wu, M., Fang, W. P., Yang, Y. Q., 2012. Promoting effect of SiO2 on the K2WO4/Al2O3 catalysts for methanethiol synthesis from methanol and H2S. Catal Commun. 22, 48-51.).
Methionine lyase has a wide range of applications in medical field, and can be used as the enzymic preparations in cancer adjuvant therapy. By adding it to diet of cancer patient, methionine in diet can be degraded, which can reduce dependence of cancer cells to exogenous methionine, so as to achieve object of adjuvant therapy (Sun, X., Yang, Z., Li, S., Tan, Y., Zhang, N., Wang, X., Yagi, S., Yoshioka, T., Takimoto, A., Mitsushima, K., Suginaka, A., Frenkel, E. P., Hoffman, R. M., 2003. In vivo efficacy of recombinant methioninase is enhanced by the combination of polyethylene glycol conjugation and pyridoxal 5′-phosphate supplementation. Cancer Res. 63, 8377-8383.); meanwhile, methionine lyase can also get into cancer cells by way of infection, causing death and serious accumulation of the cancer cells, which is a cutting-edge technology in gene therapy for cancer (Venkatachalam, K V, 2015. Novel cancer therapy: Targeting methionine metabolism. FASEB J. 29(1): 897).
Methionine lyase is widely present in protokaryon and is not yet found in fungus. Prokaryotic methionine lyase gene is hard to be expressed efficiently in eukaryotic fermentation microorganism due to codon bias problem, which restricts capability improvement of the eukaryotic microorganisms, especially some food-related fermentation microorganisms. In addition, using prokaryotic methionine lyase for cancer treatment is likely to cause immune reaction (El-Sayed, A S, 2010. Microbial L-methioninase: Production, molecular characterization, and therapeutic applications Appl Microbiol Biotechnol 86, 445-467.). Accordingly, providing methionine lyase with eukaryotic source becomes main way to overcome above problems.